1. Field of the Invention
The present invention relates to a thermoplastic resin composition having excellent abrasion resistance, excellent impact resistance, and a high critical PV value. More specifically, it relates to a critical PV value. More specifically, it relates to a thermoplastic resin composition containing fine powder particles of ultra-high molecular weight polyolefin (e.g., polyethylene). The present invention also relates to modified ultra-high molecular weight polyolefin powder having good affinity to and dispersibility in thermoplastic resins and good adhesion properties to metals and resins.
2. Description of the Related Art
Thermoplastic resins having excellent mechanical strength and abrasion resistance, such as polyamides, polyacetals, polyesters, and polycarbonates, have been heretofore used for mechanical parts such as bearings and gears. However, these thermoplastic resins have disadvantages in that, when compared with conventional metallic materials such as brass and other copper alloys, their critical PV value (i.e., the critical value of a load at which a bearing material will heat-melt and seize at a constant load (P) and velocity (V), or more) is low.
Various attempts have been made to improve the critical PV values of the above-mentioned thermoplastic resins. For example, Japanese Examined Patent Publication (Kokoku) No. 46-41456proposes the blending of the thermoplastic resins with powdered high density polyethylene, to improve the critical PV values. However, in the above-mentioned blended thermoplastic resins, there remain the disadvantages of poor dispersibility in the thermoplastic resins, an insufficient improvement of the critical PV values, and poor mechanical strength, due to the high viscosity and large particle sizes of these materials.